The present invention relates to a ribbon drive clutch for use in typewriter equipment to alternately drive a printing ribbon and an error correction ribbon.
The development of high speed typewriter equipment and the development of error correction ribbons for use in such typewriter equipment has resulted in a need for a simple, effective ribbon drive apparatus which is capable of driving either a printing ribbon or an error correction ribbon.
The prior art related to ribbon drive apparatus includes the devices shown in U.S. Pat. No. 3,026,987 to Gather, U.S. Pat. No. 3,948,382 to Nesbitt et al., and U.S. Pat. No. 3,954,167 to Kranz et al. The deficiencies of these devices is related to their use of gear trains which are shifted by a reversing stepper motor to drive a gear train in an opposite direction. The use of gear trains in the above devices results in inaccuracy of operation due to wear of the gear teeth and possible damage due to dirt or other foreign matter falling into the gear train, especially when such devices are operated at relatively high speeds. In addition, the use of gear trains results in a need for a relatively high degree of accuracy in the manufacture of the gears, the gear plates, and the bearings on which the gears are mounted. This results in a generally complex and costly assembly.